This invention relates to a holding device for a linear guide rail applied to a machining center or a lathe for slidably guiding a machine tool or the like in the longitudinal direction thereof.
A linear guide rail R for slidably guiding a machine or the like in the longitudinal direction thereof as shown in FIG. 19 is widely used as a machine element. When the linear guide R is installed, it is positioned in contact with a vertical reference face L extending vertically from an installation surface f, and a plurality of bolts j are threaded into corresponding threaded holes i formed in the installation surface f through holes h formed through the guide rail R at specified intervals and having a large diameter.
In such a configuration, however, even if the vertical reference face L has an even and uniform surface, the guide rail R may not snugly fit against the reference face L for the following reasons:
(1) Inherent distortion of the linear guide rail R from linearity.
(2) Design tolerance of the threaded holes i
(3) Deformation of the bolts j during tightening.
(4) Deviation between the positions of the holes h and their corresponding threaded holes i.
This results in low accuracy of positioning of the linear guide rail R and causes distortion in movement of the machine mounted thereon. Especially, in the case of a machine tool for precision machining, the low positioning accuracy of the linear guide rail R may lower the yield of the products and cause many other drawbacks.
In addition, the holes h must be formed through the linear guide rail R with high accuracy at positions coincident with their corresponding threaded holes i, and such machining of the holes h takes time and effort. Also the replacement or modification of the linear guide rail R cannot be made quickly because of the machining process. Furthermore, in fixing the linear guide rail R, the holes h are aligned with the corresponding threaded holes i and the bolts j are sequentially threaded into the corresponding threaded holes i from above. This also takes time and effort.
In order to overcome the above drawbacks, the use of pressing means has been proposed. The pressing means comprises a screw receiving projection k (see FIG. 19) formed in parallel to the vertical reference face L on the installation surface f of the base and having a plurality of threaded holes formed therethrough in a direction perpendicular to the longitudinal direction thereof, and a plurality of fixing bolts. When the fixing bolts are threaded through the threaded holes, the forward ends of the fixing bolts press the linear guide rail R against the vertical reference face L and straighten it. In this configuration, however, the screw receiving projection k must be formed on the base, which requires special processing work. Also, the fixing bolts must be threaded in parallel to the horizontal surface of the base. In some cases, it is impossible because of the presence of other machine elements or other reasons. Thus, the means is not necessarily suitable for practical use.
As means to solve the problems, a holding device for positioning is proposed in Japanese Patent No. 2709416. The holding device comprises an eccentric pressure contact plate engageable with one side of a linear guide rail to press the other side thereof against a vertical reference face L, a revolving shaft part which has a tool hole, a vertical slot and a female thread with a pressure surface edge on its bottom end along its central axis and which can be snugly fitted in an insertion hole formed in an installation surface of a base, and a pressure screw having an operating groove in one end for pressing the pressure surface edge of the revolving shaft part downward to extend the slit portion of the revolving shaft part outward when it is threaded downward.
In this configuration, the revolving shaft part is fitted in the insertion hole, and a tool such as a hexagonal wrench is inserted in the tool hole in the top of the eccentric pressure contact plate and rotated to rotate the eccentric pressure contact plate. Then, the distance from the revolving shaft part to a position where the pressure contact plate meets the linear guide rail is varied since the pressure contact plate has an eccentric shape. Thereby, the peripheral face of the eccentric pressure contact plate is pressed against a side of the linear guide rail.
The above configuration has the following problems.
1) The slit portion of the revolving shaft part is extended outward and brought into pressure contact with the internal face of the insertion hole, whereby the eccentric pressure contact plate is secured. Thus, when a force which is larger than the pressing force is applied to the pressure contact plate, the center of the revolving shaft part is shifted, and the linear guide rail cannot be sufficiently held.
2) The female thread is formed below the tool hole in the revolving shaft part. Thus, after a tool has been inserted into the tool hole and the eccentric pressure contact plate has been rotated to a pressure contact position, the tool must be removed and a screw driver must be inserted through the tool hole into the operating groove formed in the top of the pressure screw to rotate the pressure screw. The eccentric pressure contact plate is likely to be rotated in reverse by a reaction force when the tool is removed. When the eccentric pressure contact plate is rotated in reverse, the pressing operation must be performed once again.
3) The slot, the tool hole and the female thread must be formed in the revolving shaft part in succession, and the operating groove must be formed in the top of the pressure screw. It takes time and effort to produce the parts.
The present invention has been made to solve the above problems and it is, therefore, an object of the present invention to provide a holding device suitable for positioning a linear guide rail.
In accordance with one aspect of the present invention, there is provided a linear guide rail holding device for holding a linear guide rail along a linearly extending vertical reference face formed on an installation surface, said linear guide rail having a first side and a second side opposite to said first side, said holding device comprising:
a pressure contact plate rotatable about a rotational axis thereof and having a lower surface engageable with said installation surface, an upper surface, and a peripheral side surface formed between said lower and upper surfaces, said peripheral side surface having an engaging face pressingly engageable with said first side of said linear guide rail to press said second side thereof against said vertical reference face,
said pressure contact plate being shaped such that the distance from said rotational axis to said engaging face gradually increases in a circumferential direction of said engaging face,
a circular boss formed on said lower surface of said pressure contact plate and having a central axis coinciding with said rotational axis,
a screw insertion hole formed along the central axis of said circular boss, and
a screw insertible through said screw insertion hole,
said installation surface having a fitting hole including a circular boss hole into which said circular boss is fittingly eangageable and a female thread hole which is formed coaxially with said circular boss hole and with which said screw is threadedly engageable.
In the above configuration, the circular boss of the pressure contact plate is fitted in the circular boss hole formed in the installation surface, and the pressure contact plate is rotated in the direction to increase the distance from the center of the circular boss to the point where the engaging face meets the linear guide rail. Thereby, the engaging face is brought into pressure engagement with the first side of the linear guide rail to press the second side of the linear guide rail against the reference face. Then, the fitting screw is inserted into the screw insertion hole through the counterbore and tightened with a screwdriver to bring the head of the screw into pressure contact with the bottom of the counterbore. Thereby, the pressure contact plate is fixedly secured by the screw to the installation surface with the engaging face in engagement with the first side of the linear guide rail. In this state, a reaction force is constantly applied to the pressure contact plate. However, since the circular boss is snugly fitted in the circular boss hole and supports the reaction force, the load applied to the screw is low and the screw is prevented from being deformed. Thus, the linear guide rail can be held straight along the reference face.
In another aspect, the present invention provides a linear guide rail holding device for holding a linear guide rail along a linearly extending vertical reference face formed on an installation surface, said linear guide rail having a first side and a second side opposite to said first side, wherein said installation surface is provided with an abutting face extending in parallel with said reference face to define therebetween a space in which said linear guide rail is positionable, said holding device comprising:
a pressure contact piece rotatable about a rotational axis thereof and having a lower surface engageable with said installation surface, an upper surface, and a peripheral side surface formed between said lower and upper surfaces,
said peripheral side surface having a first engaging face and a second engaging face opposite to said first engaging face with respect to said rotational axis such that said first and second engaging faces are pressingly engageable with said first side of said linear guide rail and said abutting face, respectively, to press said second side of said linear guide rail against said vertical reference face,
said pressure contact piece being shaped such that the distance from said rotational axis to at least one of said first and second engaging faces gradually increases in a circumferential direction thereof,
a screw insertion hole formed in said pressure contact piece and coinciding with said rotational axis, and
a screw insertible through said screw insertion hole,
said installation surface having a female threaded hole between said vertical reference face and said abutting face with which said screw is threadedly engageable.
In the above configuration, a reaction force is not supported by a circular boss as in the case of the invention of the first aspect of the present invention but by the abutting face in engagement with the second engaging face of the pressure contact piece. Thereby, the linear guide rail is held in pressure contact with the vertical reference face.